1. Field of the Invention
The present invention relates generally to a method and container for growing transplantable plants, and more particularly, to a method and container for growing plants such as trees and shrubs for transplanting.
2. Description of the Prior Art
Plants, such as trees and shrubs, which are intended to be transplanted are commonly grown above ground in containers. Such containerized plants can be grown at a faster rate than those grown in the ground, they are more easily tended, and because the roots of the plants are not severed when the plants are transplanted, transplanting is more often successfully accomplished.
Various types of containers have been used for growing plants, i.e., for retaining the soil and roots of plants prior to transplanting. For example, metal cans and cylindrical plastic containers with holes in the bottoms were among the first plant growing containers used. The problem with such cylindrical containers is that as roots grow outwardly and downwardly within the containers, the sides and bottoms of the containers cause spiral and circular root growth. Spiral and circular root growth is damaging to plants in that such root growth does not provide lateral anchorage for the plants when transplanted, and the spiraled and circled roots do not extend into the soil to gather nutrients.
Cylindrical containers having holes in the sides to terminate spiral and circular root growth have also been utilized. The side holes or openings function to cause air-pruning of the roots, i.e., when a root extends into the vicinity of an opening whereby it is exposed to the atmosphere, the growth of the root stops. While the use of cylindrical containers with side holes reduces the incidence of spiraled and circled roots, some spiraling and circling still take place.
Transplantable landscape plants have also been grown in square, bottomless containers placed on wire screens whereby roots reaching the bottom of the container are air-pruned. Most of the root tips produced end up at the bottom of such containers, and the requirement of placing the containers on wire screen surfaces generally makes the practice uneconomical.
Recently, containers have been developed for controlling spiral and circular root growth whereby the root tips are physically trapped by surfaces in the container and are prevented from elongating, or the spiraling and circling root tips are caused to pass through vertical openings in the sides of the container whereby the tips are air-pruned. Such a root trapping type of container is described in U.S. Pat. No. 4,442,628 issued Apr. 17, 1984. A container including vertical side wall openings for air-pruning spiraling or circling roots is described in U.S. Pat. No. 4,497,132 issued Feb. 5, 1985.
Most recently, containers have been developed (see U.S. Pat. No. 4,716,680 issued Jan. 5, 1988) comprised of removably joined rectangular side panels which form a rectangular open-topped container. The interiors of the side panels include lattices of root trapping recesses having pointed ends for directing roots whereby they become trapped. The trapping of the roots causes the growth at the ends to terminate and lateral root growth to develop. The side panels can be disconnected and moved laterally apart to prevent damage to the root tips trapped in the recesses. While such root trapping containers formed of removably joined side panels can be used successfully, they suffer from the disadvantage that different sizes of side panels are required for different sizes of containers.
By the present invention, an improved method and container for growing a transplantable plant are provided which obviate the various problems mentioned above.